Oxidation of saturated aliphatic hydrocarbons to ketones



United States Patent O OXIDATION OF SATURATED ALIPHATIC HYDRO- CARBONS TO KET ONES Nat C. Robertson and James H. Gardner, Cambridge, and Albert Di Nardo, Jamaica Plain, Mass., assignors, by mesne assignments, to Escambia Chemical Corporation, Pace, Fla., a corporation of Delaware Application September 2, 1952, Serial No. 307,414

4 Claims. (Cl. 260S97) This invention relates to the production of chemicalsA and more particularly to the production of oxygenated hydrocarbons by the air oxidation of normally gaseous saturated hydrocarbons.

A principal object of the present invention is to provide a process for the oxidation of normally gaseous saturated hydrocarbons to produce high yields of ketones.

Another object of the invention is to provide a process of the above type which is particularly adaptable to the production of high yields of acetone.

Still another object of the invention is to provide a process of the above type which provides for the selective oxidation of normally gaseous saturated hydrocarbons, having one tertiary hydrogen atom, in such a way that there is no net yield of the expected tertiary alcohol.

Still another object ofthe present invention is to provide an improved process for the oxidation of isobutane in which there is no net yield of tertiary butyl alcohol.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others which are exemplified in the following detailed.

disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description and the accompanying drawing which is a diagrammatic ow sheet illustrating one preferred method of practicing the invention.

In the present invention a normally gaseous saturated hydrocarbon, containing one tertiary hydrogen atom, is oxidized at a relatively high pressure to produce predominantly ketones as final reaction products. The method comprises the steps of dissolving the gaseous hydrocarbon in a tertiary alcohol. In a preferred embodiment of the invention the normally gaseous hydrocarbon is isobutane and the solvent is tertiary butyl alco hol. To accomplish the oxidation an elemental-oxygencontaining gas is passed through the solution while the solution is held under pressure. During oxidation the solution is maintained at a temperature above about 145 C., while the oxygen-containing gas passestherethrough. Thereafter the oxygenated hydrocarbons are separated from the solution.

While the oxidation of normally gaseous saturated hy# drocarbons in solution is not new, it has been found that the method of practicing the present invention provides particularly alvantageous results, since ketones rather than alcohols are the final reaction products. -When isobutane is oxidized in a solvent such as benzene, the principal reaction product is tertiary butyl alcohol. However, when tertiary butyl alcohol is employed as the solvent, it has been found that there is no net gain of tertiary butyl alcohol, the final reaction product comprising primarily ketones and, in particular, acetone.

While the invention will be specifically described here- ICC inafter as applied to the oxidation of isobutane, it is equally applicable to other hydrocarbons having one tertiary hydrogen atom. One preferred embodiment of the invention is set forth in the following nonlimiting example.

` Example I Thirteen hundred grams of tertiary butyl alcohol together with 1.4 grams of manganous propionate and 40 cc. of a pH 5 phosphate buffer solution are charged to a high pressure reactor 10. Eight hundred and fifty grams of isobutane are passed through the reactor and the reactor temperature is raised to 125 C. Air is fed until the pressure reaches 690-710 p. s. i. the temperature being raised to l75-l80 during this addition. A steady rate of air feed of about 4 standard cubic feet per hour is commenced, an automatic pressure relief valve venting nitrogen, oxides of carbon and a small amount of uncondensed reactant downstream of a condenser 12 to maintain 700 p. s. i. Isobutane is fed at varying rates to replenish the consumption. 412 grams of isobutane are fed in this manner during a six hour run.

As is apparent from a comparison of these figures with' the analysis of the product set forth above, the present invention gives a much higher yield of acetone, about twice as much as is obtained under otherwise similar conditions. obtained by the procedure of the present invention result in practically no net consumption or production of tertiary butyl alcohol. The small loss of tertiary butyl alcohol noted in the above specific analysis is of the order of handling losses.

When the process is operated on a continuous basis, the condenser 12 continuously retluxes isobutane, tertiary butyl alcohol and other oxygenated products to a water scrubber 14. The refluxed isobutane is separated from the remainder of the reflux in the scrubber 14 and is recycled to the bottom of the reactor 10. From the scrubber 14 the reflux land the scrubbing water are directed into a distillation separation apparatus 16 (which may include several conventional stills) where the contained water and various reaction products are removed from the tertiary butyl alcohol contained in the reux stream. This tertiary butyl alcohol or its water azeotrope is also recycled to the reactor 10.

As can be seen from the drawing, some of the liquid in the reactor 10 is also fed to the distillation separation apparatus 16 so as to provide for continuous removal of the variousoxygenated products which are not carried off as vapors and condensed in the reflux condenser 12.

While one specific example Yof the present invention has been given above, it is subject to wide variations Y without departing from the scope thereof. For example,

Patented Feb. 5, 1957 After termination of the run the reaction mixture isV The increased yields of acetone which are` 3 oflarge concentrationsro'f ldangerously explosive hydroperoxides. -It is Vbelieved that themetal-.walls yof.the reaction chamber may have sutlicient catalytic eiect to prevent the formation of such hydroperoxides. Similaily, while the use ofiaph'osphate .butler solution(which' isV obtainedby titrating a .solution of -tris'odiurn phosphate-with .phosphoric acid.) isquite.etfectivenumerous other Well-known buffer solutions Amay b'e employed. The range of operating pressures and operating tempera# tures is quite broad and canbevaried within considerable limits..

Withregardto pressure it should .bepointed out.y that itfis preferably. maintainedabove 3'00. lbs.,per.-` square inch, but.;tha`t considerably `higher kpressures may be .utilized where design considerations indicate the. desir'aljility. of such higher pressures. The temperature within the .re-- actor-.10"maylbe variedbetween about 145 C..and about 200' "CL for higher. 'The same generalv conditions apply, with respect .to rates of'feed of. the constituents. into .the reactor. About the only limitations uponsuch feedfare the diiculty oftemperature controland the undesirability of,permitting any .appreciable concentrations ofV oxygen in thespace above the liquidphase. 4The presence o'foxygen in this space would constitutea deliniteoperating hazard.

While the `above invention Vhas been specifically described` in termsof the oxidation ofv 4isobut'ane, it is equally applicable. to other hydrocarbons of molecular WeightofC or less containing only one tertiary hydrogen atom.V such asisopentane or isooctane. Equallygthe tertiary alcoholhasibeen described as tertiary butyl alcohol.` This maybe replaced-by the tertiary alcohol'normally constituting -the rst reaction product of, for example, the Yisopentane or the isooctane. In these latter two .cases the tertiary alcohols would be tertiary amyl alcohol and 2,2,4-trimethyl-pentanol-4, respectively.

vSincecertain.changes may be made vin the above processr without. departing from the scope of the invention herein .involved,\it .is intended vthat allmatter contained in-.theabove description, or shown in the accompanying` drawing, .shall beinterpreted as illustrative and not in Va. limiting sense.

What is claimed is:

l. A. .method of voxidizing 4a--satu11ated .hydrocarbon having from 4 to 8 carbon atoms and containing at least one tertiary hydrogen atom" to produce ketones which comprises dissolving said saturated hydrocarbon in a tertiary alcohol having thesame number of carbon atoms as said saturated hydrocarbon, passing an elementaloxygen-containing H(pas through .said vsolution while said solution is held under pressure, maintaining said solution at a temperature. abovewabout -145" C. While said gas.

passes therethrough, and separating 'ketones fr'omfsaid solution.

2; A method ofroxidizingisobutane toproduceav high yield of acetone with essentially no net production of tertiary butyly alcohol which comprises dissolving"'isobutane in tertiaryhutylalcohoh. passing. an elementaloxygen-containing gas through said solution while said solution is held under pressure, maintaining said solution at a temperature :above about v145 1C. while'said .gas

passes therethrough, and "separatingracetone .fromszitl t solution.

3. The method of claim 1 whereinesaid-saturat'ed hydrocarbonf is isooctane l and :saidV 'tertiary` alcoholis 122,4- trimethyl-pentanol-4.

4. The Vmethod ofuclaim -l iWhereinsaid `saturatedihydrocarbon is `isopentane` kand vsaidftertiary alcohol' is a tertiary a'myl alcohol.

References Citedfin the tile oithis patent UNITED STATES vPATENTSV 

1. A METHOD OF OXIDIZING A SATURATAED HYDROCARBON HAVING FROM 4 TO 80 CARBON ATOMS AND CONTAINING AT LEAST ONE TERTIARY HYDROGEN ATOM TO PRODUCE KETONES WHICH COMPRISES DISSOLVING SAID SATURATED HYDROCARBN IN A TERTIARY ALCOHOL HAVING THE SAME NUMBER OF CARBON ATOMS AS SAID SATURATED HYDROCARBON, PASSING AN ELEMENTALOXYGEN-CONTAINING GAS THROUGH SAID SOLUTION WHILE SAID SOLUTION IS HELD UNDER PRESSURE, MAINTAINING SAID SOLUTION AT A TEMPERATURE ABOVE ABOUT 145*C. WHILE SAID GAS PASSES THERETHROUGH, AND SEPARATING KETONES FROM SAID SOLUTION. 